This invention relates to a positioning method and apparatus using a stepper motor for moving an object to a specified position, and particularly to a positioning method and apparatus suitable for a magnetic disc drive unit.
A conventional magnetic disc drive unit based on the stepper motor positioning system has employed a unidirectional excitation system in order to eliminate the hysteresis effect of the stepper motor in coping with an increased track density, as described in U.S. Pat. No. 4,490,662 (corresponding to JP-A-58-29397). For the enhancement of the positioning accuracy of the above system, a method of temporary stoppage before the target position was proposed in U.S. Patent Application Ser. No. 009,072 (corresponding to JP-A-61-84713). These systems are both intricate in their logical operating manners and insufficient in the compensation for a prolonged access time. U.S. Pat. Nos. 4,489,259 and 4,437,049 also disclose stepper motor positioning systems.
The above-mentioned prior art systems do not deal with the reduction of access time of the positioning mechanism.